A) Field of the Invention
This invention relates to an audio signal processing apparatus and more specifically to an audio signal processing apparatus that mixes audio signals input from a plurality of input channels and outputs the mixed audio signals.
B) Description of the Related Art
Normally an audio signal processing apparatus having a plurality of input channels such as a mixer adjusts or sets parameters for each channel. The audio signal processing apparatus has operators for setting parameters for each input channel. For example, the apparatus has various setting operators such as a fader operator for adjusting a volume level, an ON-key for setting on/off of the input channel, a PRE-key for setting whether or not an input signal is output via the fader, etc. A plurality of the setting operators are positioned on a panel surface of the audio signal processing apparatus.
The fader operator is an operator for continuously changing parameters of each input channel and adjusts an input level (volume level) of each input channel. The ON-key is a switch equipped to each input channel and switches connection (ON) and disconnection (OFF) of an output path from each input channel to various buses such as a mixing bus, a stereo bus, etc. This function is generally called an ON/OFF function. The PRE-key is a switch equipped to each input channel and selects an audio signal input to various buses from a pre-signal and a post-signal. The pre-signal is a signal bypassing the fader, that is, a signal before a volume level of which is not adjusted by the fader (pre-fader). The post-signal is a signal via the fader, that is, a signal after a volume level of which has been adjusted by the fader (post-fader).
Generally, as described in the above, parameters of each channel are adjusted and set channel by channel; however, a function in which a plurality of input channels are grouped and parameters of the input channels belonging to one group are adjusted all together has been known. In this specification, a group of input channels in this function is called a digitally controlled amplified (DCA) group. Moreover, a function for adjusting volume levels (input levels) of the grouped input channels all together is called a DCA function in this specification.
For the DCA function, at least a fader operator (DCA fader operator) and a DCA mute key for each DCA group are equipped. The DCA fader is an operator for adjusting input levels of channels in one DCA group all together and able to continuously change the input levels as well as the above-described fader operator for input channel. The DCA mute key is a switch for turning on or off a DCA mute. The DCA mute is a function for instantly declining a value of the DCA fader to minus infinity decibel (−∞dB). “PM5D/PM5D-RH MANUAL”, YAMAHA CORPORATION, 2004 discloses the DCA function.
Although both DCA mute function and ON/OFF function of input channels are a function for muting (controlling an output of an input channel not to supplied to various buses), results of executing the functions are slightly different from each other because of their ways to accomplish the muting are different.
The ON/OFF function of input channels switches between connection (ON) and disconnection (OFF) of an output path from input channels to various buses; therefore, both pre-signal and post-signal are muted.
On the other hand, the DCA mute function mutes the post-signal but does not mute the pre-signal. That is, an input channel set of which pre-signal is selected to be output is transmitted to a mix bus even if the DCA mute function is executed. That is because the DCA mute function just sets a fader level of the input channel to “−∞dB”, and the pre-signal, bypassing the fader, is not affected by the fader level. In the conventional technique, the DCA function is considered to be a function for collectively controlling fader levels of input channels.
However, the DCA function may have been considered as a function for collectively operating input channels. A user thinking that way tends to misunderstand that the DCA mute can mute all the input channels belonging to one DCA group regardless of the selection of the pre-signal and the post-signal. Therefore, the user may think that an operability of an apparatus is inferior because the pre-signal is not muted by the DCA function, and that type of misunderstanding may lead a mistake in a real time performance.